Highly effective, alarm alerts you to any unauthorized exits/entries through emergency exit doors and rear doors. Serves as an inexpensive security device and helps stop theft as well. The unit uses a momentary switch. After initial installation, unit is always on and you do not have to remember to turn it on when you leave a protected area.This model also eliminates having to remember to re-arm it because it is never off. When the alarm is triggered, to silence the alarm, insert the key and turn completely to the inchRESET inch position and hold for 2 seconds, then release. The switch will spring back to its original position and push the key out. To turn the unit off, supply power must be removed.